1. Field of the invention
The present invention relates to a refrigeration cycle apparatus.
2. Description of Related Art
In a conventional refrigeration cycle apparatus having a gas-liquid separator which separates the liquid coolant from the gas coolant, there are two refrigeration types. One is called a receiver cycle and the other is called an accumulator cycle. FIG. 14 and FIG. 15 are schematic views of the receiver cycle and the accumulator cycle, respectively.
With reference to FIG. 14, an operation of the receiver cycle is explained in the order of a coolant flow. The liquid coolant provided from a receiver 3 is intensively expanded by an expansion valve 4 and introduced into an evaporator 5 as a misty condition of a low temperature and a low pressure. The misty coolant introduced into the evaporator 5 is evaporated to be the a gas coolant of super-heat condition by receiving a latent heat from an atomoshperic air around the surface of the evaporator 5 so as to cool the air while passing through the evaporator 5. Then the gas coolant is sucked into a compressor 1. Such gas coolant is compressed to a high temperature and high pressurized condition and discharged from the compressor 1 to a condenser 2 in which the gas coolant is liquidized. The liquidized coolant flows into a receiver 3. The refrigeration is achieved by repeating the above-mentioned operations.
An operation of the accumulator cycle is explained in the order of a coolant flow by using FIG. 15. The gas coolant is sucked into a compressor 1 and compressed therein to a high temperature and high pressurized condition, and such compressed gas is discharged from the compressor 1. The discharged high-temperature and high-pressure gas is introduced into a condenser 2 and is changed into the liquid coolant because of the forcibly cooling. Such liquid coolant becomes a super-cool condition after the same is passed the condenser 2. The liquid coolant liquidized by the condenser 2 flows into a capillary tube 6a of a composite-throttling-device 6. The shape of the capillary tube 6a is so small that the pressure of the coolant is reduced. The coolant is rapidly expanded by passing through a nozzle 6b so that it becomes a low-temperature and low-pressure misty coolant. The misty coolant flows into an evaporator 5 in which the coolant is evaporated by receiving the latent heat for evaporation from an atmospheric air around the surface of the evaporator 5. Therefore, the air passing through the evaporator 5 is cooled. After such evaporation, the coolant flows into an accumulator 7 in which the coolant is separated into the liquid coolant and the gas coolant so as to transfer only the gas coolant into the compressor 1. The refrigeration is achieved by repeating the above-mentioned operations.
According to the above-explanation, it is necessary to properly control the coolant condition of the outlet portions of two heat-exchangers, namely, the condenser 2 and the evaporator 5 in the refrigeration cycles for effectively operating the refrigeration cycles.
The difference between the receiver cycle and the accumulator cycle exists in the control method of the coolant condition of the outlet portion of the condenser 2 and the evaporator 5, as shown in FIG. 16. Hereinafter, each control method is explained.
According to the receiver 3 cycle, the receiver controls the coolant condition at the outlet portion of the receiver 3. Namely, since an interface between gas and liquid always exists in the receiver 3 and since only the saturated liquid coolant is sent out from the receiver 3, the coolant at the outlet portion of the condenser 2 always keeps in the saturated liquid condition. In this cycle, the expansion valve 4 controls the coolant condition at the outlet portion of the evaporator 5. Namely, in response to a signal from a heat detector 4a located the outlet portion of the evaporator 5, the expansion valve 4 controls the flow rate of the coolant so that the gas coolant of the outlet portion has a constant super-heat(SH). Therefore, the gas coolant having a controlled super-heat is constantly sucked into the compressor 1.
On the other hand, according to the accumulator cycle shown in FIG. 15, the composite throttling device 6 is provided in the upstream of the inlet portion of the evaporator 5 while no receiver is provided in the downstream of the condenser. Although the coolant condition at the outlet portion of the condenser 2 changes, a super-cool(SC) is controlled with a certain degree because a flow characteristic of the composite throttling device 6 is set so that the liquid coolant constantly flows through the composite throttling device 6.
The coolant condition of the outlet portion of the evaporator 5 is controlled by the accumulator 7 in a way that an interface between gas and liquid exists as well as the receiver 3 in the receiver cycle in FIG. 14 and that only a saturated gas coolant is sent out to the compressor. As a result, the coolant of the outlet portion of the evaporator 5 is constantly kept in a saturated gas phase condition.
However, there are problems about the above two types refrigeration cycle apparatus.
In the receiver cycle shown in FIG. 14, there are two following problems. First of all, a high pressure container having a high pressure resistance is necessary for the receiver 3 because it is arranged in the downstream of the condenser 2, which is a high pressure area. In the second, the apparatus does not properly carry out at the start of the refrigeration cycle because the liquid coolant exists in the receiver 3 which is far from the suction portion of the compressor 1 according to the configuration of this cycle.
On the other hand, according to the accumulator cycle shown in FIG. 15 which uses the composite-throttling-device 6, there is a problem that a large-sized tank is necessary for because it separates the gas coolant from the high pressurized liquid coolant. Furthermore, there is a necessity that the contained coolant volume can not be checked by a sight glass provided on the gas-liquid separator such as the receiver 3 in the receiver cycle.